The present invention relates to a tool for use in replacing a chain connecting a pair of sprockets in a drive system.
In many chain drive systems having a pair of sprockets drivingly connected by an endless chain, only one of the two sprockets is readily accessible. In such a system, it is advantageous to be able to replace the chain without having to access the more difficult-to-reach sprocket. The foregoing considerations apply particularly to the replacement of a timing chain in an overhead cam automotive engine, where access to the driveshaft sprocket in the engine may require removal of the radiator, water pump, oil pump, smog control equipment, etc., and may even require complete engine removal.
In replacing a timing chain in an overhead cam engine, it is essential to maintain the rotational relationship between the driveshaft sprocket and the camshaft sprocket. This can be done by opening the timing chain at a point near the top of the camshaft sprocket, through disconnecting the typical disconnect joint therein, and by connecting the disconnected chain ends to the two disconnected ends of a replacement chain, to form a double-length endless chain. The engine is then turned over slowly, while maintaining the double-length chain in engagement with the camshaft sprocket, until the positions of the two chains have substantially been transposed. The old chain is then disconnected from the replacement chain, and the free ends of the replacement chain are connected to complete the operation.
Heretofore, the above-described transposition of the old and new timing chains has been somewhat difficult, requiring the operator to keep the combined, double-length chain engaged at all times with the camshaft sprocket, and at the same time, to keep the loose portion of the double-length chain from becoming tangled or caught on an engine part. If chain tangling occurs, the moving chain may be pulled off the camshaft sprocket, causing rotational misalignment between the two sprockets. Also, a chain-tensioning member in the engine may be released toward a locked, fully extended position, or the member may become partially disassembled. The amount of work required to replace the timing chain is then greatly increased, requiring the extensive engine disassembly noted above.
One object of the present invention is to provide apparatus for replacing a chain connecting a pair of sprockets, where one sprocket only is readily accessible.
Another object of the invention is to provide such apparatus constructed to overcome above-mentioned problems associated with replacement of a timing chain in an overhead cam automotive engine.
Another object of the present invention is to provide such a device which is simple and relatively inexpensive in construction.
The apparatus of the present invention includes a holder and a pair of spaced, chain abutments carried on the holder for contacting spaced regions in a connecting chain, where such is trained over an exposed portion of a sprocket. The members function to maintain engagement between such spaced chain regions and the sprocket during a chain replacement operation. An opening formed between the abutments is adapted to receive the two disconnected end portions of a replacement chain, which end portions are connected to the disconnected ends of the old chain during chain replacement. The apparatus is open on one side between the abutments to expose connecting links of a chain to be replaced to permit manipulation of the chain ends during replacement.
Chain support means are provided to support a replacement chain. One embodiment of the invention includes a position-adjustable chain-support wheel for supporting a double-length chain, formed by joining the disconnected ends of an old chain and a replacement chain, under tension during a chain replacement operation. In other embodiments of the invention, a pair of arcuate chain-supports are provided, for guiding and supporting sections of a replacement chain over opposite sides of the apparatus.
These and other objects and features of the present invention will become more fully apparent when the following detailed description of preferred embodiments of the invention is read in connection with the accompanying drawings.